How to retry only error-producing line in a function

Question

This is quite tricky to explain, but I'd like to know if there is a way to repeatedly retry only the line of code that produced the error until it works. For example say I have the code:

def unreliabelfunction():
    #Line 1 of code
    #Line 2 of code (sometimes produces an error and sometimes works)
    #Line 3 of code

#Error handling should go where function is called, rather than inside the function.
unreliablefunction()

I would like to have some sort of error handling that would continually run line 2 until it worked (without rerunning line 1) and then continue with the rest of the function. In addition, I would like the error handling to be outside of the function and not to change the function itself.

I hope this makes sense and thank for your help :)

Answer 1

You are looking for a try: except block.

Here's a rough example.

def unreliabelfunction():
    line_1()
    try_wrapper(line_2())
    line_3()

# Pass a function to try_wrapper
def try_wrapper(fn, args):
    successful = False
    while not successful:
        try:
            # Execute the function.
            fn(*args)
            # If it doesn't cause an exception, 
            # update our success flag.
            successful = True
        # You can use Exception here to catch everything, 
        # but ideally you use this specific exception that occurs.
        # e.g. KeyError, ValueError, etc.
        except Exception:
            print("fn failed! Trying again.") 

See the docs: https://docs.python.org/3/tutorial/errors.html#handling-exceptions